The agencies say long-term solutions for those living in the overcrowded camp are needed.

According to Stephen Vaughan, head of CARE Kenya, people who had fled terrible suffering are not getting the care they needed.

"As well as the human cost, there is also a cost to security in the region," he said.

"If children are not going to school and if people do not have proper shelter and other services, this has the potential to fuel further militarisation, violence and instability."

Nigel Tricks, head of Oxfam in Kenya, said: "Refugee camps are only temporary solutions and the situation is increasingly untenable. Funds are needed now to save lives, but we can't keep pumping money in year after year while the camp keeps getting bigger.

"A change in approach is urgently needed. However, right now, the world has an obligation not to turn its back on Dadaab and the needs of the people there."

Problems with security in the camp have also hampered the aid operation.

Last October, gunmen kidnapped two Spaniards working for Medecins Sans Frontieres (Doctors Without Borders) at the Dadaab camp. They are still being held hostage in Somalia.

Dadaab was founded more than 20 years ago - after Somalia first descended into chaos. It has not had a functioning central government since 1991 and has been racked by fighting between various militias.